1. Field of the Invention
The present invention relates to carpule syringes and more specifically associated syringe carpules for storing, transporting and in situ mixing of a local anesthetic, such as lidocaine, and a buffer, such as sodium bicarbonate, and delivery of buffered anesthetic solution.
2. Background Information
The present invention relates delivery of buffered anesthetic solution. As background, the essentially first “modern” local anesthetic agent was lidocaine (original trade name Xylocaine®). Lidocaine was first introduced in the late 1940s. Prior to its introduction, Nitrous oxide gas and procaine (plus alcohol in the form of whiskey) were the major sources of pain relief during dental procedures. Lidocaine proved to be so successful that during the late 1940s and throughout the 1950s that the use of procaine and nitrous oxide gas as primary anesthetic agents all but vanished. With some professionals humorously noting that whiskey survived, but it is no longer used on patients.
Lidocaine (along with all other injectable anesthetics used in modern dentistry) is in a broad class of chemicals called amides, and unlike ester based anesthetics, amides are hypoallergenic. Lidocaine sets quickly and may conventionally be combined with a small amount of epinephrine (adrenalin) to produce profound anesthesia for several hours. Lidocaine is still the most widely used local anesthetic in America today. Lidocaine conventionally comes in a variety of dosage forms, including injectable, topical jelly, and oral/topical viscous solution. Common strengths are 1%, 2% and 4%. The percentage of lidocaine is an indication of the total by weight percent, such that one percent lidocaine means that there is one gram of lidocaine in one hundred total milliliters of liquid solution.
In order to alleviate the pain experienced by local anesthetic injections medical professionals often add sodium bicarbonate (NaHCO3) to the selected anesthetic in order to alkalize the medication. Several articles have been written on the subject matter such as follows: Christoph R. A. Buchanan L., et al.: Pain Reduction in Local Anesthetic Administration Through pH Buffering. Annal of Emerg Med 1988. 17, 117-120.; Stewart J. H. Chinn S. E. et al.: Neutralized Lidocaine with Epinephrine for Local Anesthesia. J. Dermatol Surg Oncol 1990. 16, 842-845; Steinbrook R. A. Hughes N. et al.: Effects of Alkalinization of Lidocaine on the Pain of Skin Infiltration and Intravenous Catheterization. J. Clin Anesth, 5 November/December 1993, 456-456; Armel H. E. and Horowitz M., Alkalinization of Local Anesthesia with Sodium Bicarbonate-Preferred Method of Local Anesthesia. Urology. 1994. 43, 101; and Suraj Achar, M.D. and Suriti Kundu, M.D., Principles of Office Anesthesia: Part I. Infiltrative Anesthesia, Am Fam Physician. 2002 Jul. 1; 66(1):91-95.
A substantial drawback of buffering anesthetics is the substantial decreased shelf life of the resulting buffered anesthetics. Buffered anesthetics left on the shelf may not be effective after one week. Thus it has become common for professionals to undergo the time consuming process of buffering the anesthetic solution on site immediately prior to giving the injection. The medical professional will often attempt to mix about nine parts lidocaine solution (typically 1 to 2 percent) to about one part sodium bicarbonate solution (8.4 percent) in a syringe or anesthetic bottle just before the procedure. The 8.4% sodium bicarbonate solution is a commonly available strength which has 8.4 grams of sodium bicarbonate per one hundred total milliliters of liquid solution.
Syringes are commonly used, for example in the fields of medicine and dentistry, to deliver controlled quantities of fluids, typically liquids, to desired locations. One well-known type of hypodermic syringe is a carpule syringe 50 shown in FIGS. 4A-C and is specifically designed for dispensing fluid from a certain type of fluid container referred to in the art as a “carpule”, such as those carpules 10 according to the present invention shown in FIGS. 1A-3B.
The conventional carpule syringe 50 and associated carpules further include U.S. Pat. No. 5,542,934 (multiple carpule syringe design); U.S. Pat. Nos. 5,330,440; 5,269,766; 5,112,307; 4,931,040; 4,919,657; 4,915,701; 4,490,142; 4,333,457; 3,848,593; and 2,671,450. These patents are incorporated herein by reference.
The conventional carpule syringe 50 includes the handle portion 52 which includes a finger grip and guard 54 and spring biased axially moveable piston engaging rod 56 as best shown in FIG. 4B. The conventional carpule syringe 50 further includes a tubular body or frame 58, sometimes called a barrel, that receives the carpule therein. The frame 58 is typically open on the side to receive a carpule therein, although rear loading carpule syringes 50 are also known. On a forward end of the frame 58 is a needle hub 60 that typically threadingly engages a needle. The conventional needle is attached to the hub 60 includes a rear piecing portion extending into the carpule through a sealed end thereof. The carpule syringe 50 will often include a removable needle guard 62 that can minimize accidental “sticking” incidents.
A carpule within the meaning of this invention is a hollow tubular device filled with medicament, or other material, to be dispensed through a needle attached to a carpule syringe, and wherein the carpule is configured to be received within the frame 58 of a carpule syringe 50, and has an axially movable plunger therein to be engaged and moved by with the rod 58 of the carpule syringe and a seal configured to be pierced by a rear piercing portion of the needle coupled to the needle hub 60.
There remains a need in the art to for a simple to operate, intuitive, accurate, cost effective apparatus and method for storing, transporting and in situ mixing of lidocaine and sodium bicarbonate and for delivery of buffered anesthetic solution.